I'm always telling audiences that David Cameron is a bright young man with prospects, who never says anything stupid. So naturally I'm puzzled this morning about William Hague's trip to Brussels.

I had assumed that Cameron's threat to take the Tories out of the European People's party (EPP) at the Strasbourg parliament was just a bit of red meat thrown to his party's intransigent core vote – to keep the troops happy while he set about making them electable.

Yet, as Ian Traynor reports today, last night party officials announced that the shadow foreign secretary had been sent to the capital of what Mrs T used to call "the Belgian empire" to inform EPP chiefs that, yes, Dave, intends to set up his own Euro-partyette, just like he said.

Hague, cleverer than Cameron but not so emotionally intelligent, was always a conviction Eurosceptic. Fat lot of good it did him with his daft "save the pound" campaign in 2001. Little did he – or anyone else – know the pound was being quietly rogered behind the White Cliffs of Dover, in the City, not in Brussels.

Yet the word was that when Hague was dispatched around EU capitals to drum up support for a less federalist conservative grouping he didn't get much support – except from fringe headbangers and the Czechs ("a faraway country") – and was looking for a way out. That's what pro-EU Tory MPs assured me.

It's true that Cameron is a "Thatcher's child" Tory who believes the hair-raising narrative of the later Maggie years whereby she was cheated into signing the Single European Act of 1986 that created the single market. She was doubtless also told the Channel tunnel would link up with Washington, not Calais, I expect.

But rhetoric designed to buy time while Dave negotiates the centre ground is one thing. Actually cutting oneself off from the largest Strasbourg group – 37% of MEPs belong to the EPP, including the parties of Merkel, Sarkozy and Berlusconi – strikes me as, well, seriously stupid.

It's not that I admire the EPP or its works. It's not that I think the EU has had a very good recession so far; too smug about it being an Anglo-Saxon banking crisis, still too cautious about digging the eurozone's way out of trouble. It's not that I'd have voted yes to Billy Hague's nightmare: the euro. Not for us anyway.

What's more, Declan Ganley, the man who blocked Ireland's adhesion to the Lisbon treaty, has since set up another new party designed to save us from ourselves. When I heard Ganley's delightfully muddled blarney in London last year I decided that's what he'd do next, silly chap.

It won't be easy for Libertas either, not least because – as the Guardian's diarist, Hugh Muir, was quick to point out – the name Libertas was registered with the Electoral Commission last year by friends of Ukip whose loathing of all things European except the salaries and expenses is more coherent than Ganley's: he keeps saying he's pro-European, but, Judge-like, wants an EU run by nicer people than have yet evolved.

Cameron's move would cut an incoming Tory government off from the dominant political network in Europe at a time – say next June – when he and it will both need each other to keep digging out of recession without falling into a serious, avoidable slump.

Posh boy that he is, it will also be socially distressing. Dave will find himself drinking strong lagers in the corner of the Strasbourg bar with types whom Etonians would regard as oiks, men with bright red faces, even brighter than Dave's own, and loud voices.

By comparison with some of them, the chap who carried Hague's bag on the Eurostar this week, Mark Francois, the Tory MP for Rayleigh, Europe spokesman, and one of no fewer than 32 members of the shadow cabinet, will sound positively polished.

We know that Cameron has been preoccupied with private grief lately and it might be kind to blame the mistake on that. Whatever you may think of Europe, it's the only Europe we've got – and it isn't all-powerful, it's about to show – yet again – that it's actually rather too feeble.

Oh dear, Dave, this move isn't clever and it isn't wise. When in hole, stop digging.